A regular expression; or regex, is a mechanism used to describe a text pattern. Regular expressions may be used for text searching, for example, to check whether a given text string satisfies a pattern represented by the regular expression. Each character in a regular expression may be, for example, a regular character, with a literal meaning or a metacharacter, wildcard or the like, with a special meaning. Together, these can be used to identify textual material in the text string.